@alphacentauri:
Thanks, this seems to be the first equation from 4.3.3 that is valid for altimeter setting sources up to 10.000ft (which should be sufficient for Europe) but only 5000ft above source.
According to 8168 this equation was used to calculate the "standard table" that is also valid up to 5000ft above source.
So it can't be used for higher altitudes of rather low-lying airports in mountainous areas (such as Innsbruck or Geneva) which have minimum crossing altitudes more than 5000ft above the airport.